The subject matter disclosed herein relates to gas turbines, and more specifically, to a process and system for forming holes in turbine blades.
In general, gas turbines combust a mixture of compressed air and fuel to produce hot combustion gases which flow over, and cause the rotation of, turbine blades attached to a rotor. The hot combustion gases can reach temperatures that exceed the melting point of the turbine blades and other components in the path of the hot gases. To prevent this, the turbine blades and other components in the gas path are typically constructed using high melting alloys and covered with a thermal barrier coating. In addition, the components may include air holes that allow cooler air to pass through or over the components. Upon exiting the holes the cooler air creates a continuous heat shielding layer over the components. This cool air layer acts as a heat shield by limiting the heat transfer from the hot combustion gases to the turbine blade. By limiting the heat transfer from the hot combustion gases the life of the components is increased.
However, the act of forming the air holes may itself cause problems, such as the introduction of cracks, stresses, or irregularities in the thermal barrier coating. Further, the multi-layer construction of the components may present challenges to forming the air holes due to the differing physical properties of the different layers. In addition, the component is typically a contoured shape whose three-dimensional (3D) profile may itself present challenges to forming the air holes.